MM-57477 Fix CSS for marketplace modal (#26869)

Co-authored-by: Mattermost Build <build@mattermost.com>

webapp/channels/src/sass/routes/_settings.scss

@@ -205,6 +205,11 @@
                 overflow: auto;
                 width: 180px;
                 background: var(--sidebar-bg);
+
+                .nav {
+                    position: fixed;
+                    margin: 0;
+                }
             }
 
             .settings-content {
@@ -529,11 +534,6 @@
         }
     }
 
-    .nav {
-        position: fixed;
-        margin: 0;
-    }
-
     .nav-pills {
         > li {
             margin: 0;